As information communication technology has been rapidly developed, mobile equipment, such as a laptop computer, a mobile phone, or a smartphone, is used as not only simply a wireless communication means but also a means for processing, transmitting and storing various pieces of information. In mobile equipment that performs various functions in this way, charging of power is a very important technology factor.
In general, power and a power supply circuit used to perform a power charging method for mobile equipment vary according to specification of mobile equipment. Thus, after a dedicated adaptor is connected to mobile equipment, power received from a power supply unit through the dedicated adaptor is converted and transmitted to mobile equipment.
However, in the power charging method, mobile equipment should be put into contact with the adaptor so that mobile equipment can be charged. Thus, the usage of mobile equipment is not free while it is charged.